With the proliferation of the Internet and access to various forms of media over the Internet, including music, video, graphics, movies, and the like, there have been attempts to bring high speed access to the Internet to homes and business so that they may take advantage of the offerings provided over the Internet. To provide high speed communications from remote locations to a subscriber's home, various offerings are available, including cable television, cable modems, digital subscriber lines (DSL), integrated services digital network (ISDN) lines, as well as satellite offerings. These offerings are generally offered in addition to a regular voice communication telephone line and require hardware, cabling, software, etc. in addition to regular telephone communication equipment.
With the digitalization of the telephone system, the Plesiochronous Digital Hierarchy (PDH) protocol has proliferated on the lines that connect a Telco switch to digital loop carrier equipment located in Junctor Wire Distribution Cabinets (JWICs). The telephone system is a synchronous system in which the time on the physical lines is generally uniform, ensuring that communications are sent and received at the same rate, with no fluctuation in the rate. In contrast, the Internet exists on Ethernet networks running the transmission control protocol/internet protocol (TCP/IP). TCP/IP running over Ethernet is a packet based communications system for which timing information is neither communicated nor important. As such, it has proven difficult to efficiently and effectively pass telephone communications traffic between asynchronous communications lines and synchronous or plesiochronous communications lines.
One prior solution for merging asynchronous and synchronous communications is to use two lines in which asynchronous packetized traffic is sent over an Ethernet line and non-packetized communications are transported in parallel over a synchronous or plesiochronous network. This requires installation and maintenance of two network infrastructures. Such duplicating of networks results in increased costs, increased need for hardware, and increased need for space.
In an effort to increase the availability of a single communications line to homes and businesses that handles telephonic voice, data, television, movies, music, facsimile, and other communications streams, the asynchronous Ethernet protocol has been suggested as a solution. However, in prior systems, time information from an upstream synchronous or plesiochronous network is not communicated across an asynchronous network such as Ethernet, requiring large buffers of memory to somewhat hide the frequency differences between the clock at the sending end and the clock at the receiving end of the communication. Using these buffers requires extra memory in an amount that is directly related to the frequency difference between the two clocks over the period of communication. Increased memory requirements results in increased cost for the devices used in the communications system. Using these buffers creates a need for additional processing and adds delay to the communications over the asynchronous network, reducing the quality of service and causing distortions, drop outs and failures. As such, the large buffer solution is inadequate because it cannot deliver a required quality of service of delivery of the communications. Lastly, if the period of communication is continuous, the buffers will either overrun or underrun, causing a lapse in communication.